This invention relates to release assemblies for use with clutches for manual transmissions, and particularly release assemblies for medium and heavy duty trucks.
Pull type friction clutches for medium and heavy duty trucks commonly have a release assembly with a bearing housing with a square lower portion and a release fork with machined tines. The release assembly is concentric with and circumscribes the transmission input shaft. The release assembly is axially displaced by a clutch yoke or fork in the course of disengaging and re-engaging the clutch. The yoke acts against the bearing housing to displace the bearing and release the clutch. As the release force is diminished, the spring force of the clutch acts against the yoke, through the bearing housing, to restore the yoke and the associated shift linkage to the engaged position. The machined tines engage the square lower portion of the housing, thereby preventing rotation of the housing about the transmission input shaft. Preventing rotation of the housing is necessary to ensure that the tips of the yoke engage the contact pads on the housing. The contact pads are fixed to lugs extending from the sides of the housing. The contact pads are formed of a suitable wearable material which sustains relative motion of the yoke tips without damaging the yoke tips. After a period of use, the release assembly is removed and replaced. A reason commonly necessitating the removal and replacement of the release assembly is the wearing of the contact pads.
Customer expectations of increasingly longer periods of service-free operation require improvement of the yoke to release assembly interface durability. It is also desired to eliminate the need to provide a machined interface between the yoke and the release assembly to prevent rotation of the bearing housing. While U.S. Pat. No. 5,911,296, assigned to the assignee of the present invention, discloses one approach to improving the yoke to release assembly interface durability, it does not teach how to prevent the rotation of the bearing housing without employing a machined yoke to release assembly interface.
The present invention discloses a release assembly restricting rotation of a housing of the release assembly without requiring the provision of machined surfaces on either the yoke or the release assembly.
The present invention also discloses a release assembly providing improved durability at the yoke to release assembly interface.
A clutch release assembly for use in a motor vehicle includes a bearing having an inner race and an outer race and having a release sleeve formed integral with the inner race and having an axis of rotation around which the outer race rotates relative to the inner race. A cover formed of metal receives at least in part the bearing assembly. The cover has a radially inwardly extending flange partially closing a first end. The cover has an open second end. The radially inwardly extending flange has an inner diameter sized to permit the release sleeve to pass therethrough and to prevent the bearing from passing therethrough. A housing is fixed to the second end of the cover. The housing, together with the cover, defines a cylindrical cavity therein centered on the axis of rotation. The bearing is disposed within the cylindrical cavity and is oriented to have its release sleeve extending past the radially inwardly extending flange. The housing is formed of metal. A low friction bushing is fixedly disposed within the cylindrical cavity and has an inside diameter smaller than an inside diameter of the inner race. A spring is axially disposed between the bushing and the bearing assembly. The spring is sized to engage the outer race and biases the outer race against the cover. Two L-shaped lugs are formed on opposite sides of one of the cover and the housing and extend radially therefrom. The lugs each define a circumferential engagement surface in a plane normal to the axis and face toward the bearing. An axially extending engagement surface is normal to the circumferential engagement surface wherein the tips of the arms of a clutch yoke engage the circumferential engagement surface to axially displace the release assembly. The axially extending surfaces prevent rotation of the housing by engagement with the tips of the arms.